Method of manufacturing a chip PTC thermistor

Abstract

Chip PTC thermistors that can easily be inspected the soldered portions after it is mounted on a printed circuit board and that can be used in a flow soldering process, and methods of making same. A chip PTC thermistor of the present invention includes: a first main electrode and a first sub-electrode on first surface of a cuboidal form conductive polymer having the PTC characteristics, a second main electrode and a second sub-electrode on a second surface opposite the first surface of the conductive polymer. Between the first sub-electrode and the second sub-electrode, and between the first sub-electrode and the second main electrode are electrically connecting with a first side electrode and a second side electrode, respectively.

What is claimed is:  
     
       1. A method of manufacturing a chip PTC thermistor comprising: 
       forming an integrated sheet by sandwiching a conductive polymer having PTC characteristics between metal foils having comb-shaped openings and integrating the polymer and metal foils by heat pressing, said comb shaped openings each comprising (1) a main opening and (2) a plurality of sub-openings formed perpendicular to the main opening,  
       providing through openings in said integrated sheet, said through openings penetrating through a top surface and a bottom surface of said integrated sheet,  
       providing protective coatings on said top surface and said bottom surface of the integrated sheet except an area in a vicinity of the openings,  
       forming an electrode on an inner wall of the through openings and in the vicinity of the through openings, and  
       dividing the sheet having said electrode and said through openings into pieces by cutting along lines of the sub-openings.  
     
     
       2. A method of manufacturing a chip PTC thermistor comprising: 
       forming an integrated sheet by sandwiching a conductive polymer having PTC characteristics between metal foils and integrating the sheet by heat pressing,  
       patterning the metal foils on the top and a bottom surface of said integrated sheet by etching, to form comb-shaped slits, said comb-shaped slits each comprising (1) a main slit and (2) a plurality of sub-slits perpendicular to the main slits,  
       providing through openings in said integrated sheet, said through openings penetrating through said top surface and said bottom surface of said integrated sheet,  
       providing protective coatings on said top surface and said bottom surface of the integrated sheet except an area in a vicinity of the through openings,  
       forming an electrode on an inner wall of the through openings and in the vicinity of the openings, and  
       dividing integrated sheet into pieces by cutting along lines of the sub-openings.